A variety of articles are made from fabric comprising natural fibers, e.g., cotton, flax, silk, and wool, and regenerated fibers, e.g., rayon. Natural or regenerated fabrics, especially cotton, are widely used in clothing because they are lightweight and comfortable. They are combustible, however, and articles fabricated therefrom may be used under conditions which create a risk that they will catch fire. Accordingly, various efforts have been made to make natural and regenerated fabrics more flame resistant.
One of the earliest approaches involved the application of various water soluble compounds. For example, the use of ammonium sulfate and a mixture of ammonium sulfate and ammonium phosphate are disclosed in nineteenth century patents. U.S. Pat. No. 54,382 to J. McGill (1866); U.S. Pat. No. 72,830 to A. Fell (1867). Water soluble flame retardant compounds are relatively inexpensive and provide efficient flame resistance. They also can be easily applied by impregnating the fabric with a water soluble solution of the retardant, followed by drying.
A principal disadvantage of the water soluble flame retardants, however, is that they impart a nondurable finish to the fabric which is removed during laundering and must be renewed after each laundering. This has led to widespread disregard of water soluble retardants in fabric articles, such as clothing, which may be washed many times during the course of their useful life.
This lack of durability can be improved somewhat by precipitating inorganic oxides on the fabric, for example, hydrated tungsten trioxide and stannic acid. Such finishes are semidurable, i.e., they resist from about one to fifteen launderings, and are adequate for applications such as drapes, upholstery, and mattress ticking.
Because many fabric articles, such as clothing, are subjected to many launderings, however, the emphasis has been on developing so-called durable finishes. Durable finishes may be imparted, e.g., by insoluble inorganic salts or oxides, such as antimony oxide, with a chlorinated organic vehicle, such as chlorinated paraffin. While durable finishes are in general more expensive per application, they are believed to offer overall efficiency because a single application can impart a finish that will withstand fifty or more launderings.
For many articles, cost efficiency can be achieved if the useful life of the article is long enough. It has not been fully appreciated that, as a practical matter, many articles become unacceptably soiled or worn over a relatively short time period and, for such articles, the cost of a durable finish is unacceptably high.
Durable finishes present other types of problems as well. Conventional laundering processes typically leave clothing with a durable finish in a highly wrinkled state. Accordingly, it generally is necessary to apply heavy starching when ironing in order to impart a neat appearance to the clothing.
An object of the subject invention, therefore, is to provide methods and apparatus for easily and economically imparting flame resistance to fabrics comprising natural or regenerated fabrics.
Another object is to provide such methods and apparatus whereby the treated fabric article may be more easily and economically ironed into a neat appearance.
A further object of the subject invention is to provide methods and apparatus wherein all of the above mentioned advantages are realized.
These and other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following description and upon reference to the drawings.